Why do young supernova remnants often shine strongly in X-rays?
This nebula is the product of a supernova explosion; in this section, the blast wave has encountered an area of dense interstellar gas, creating turbulence in the wave and causing it to glow. The picture is a composite of three images taken by the Hubble Space Telescope.
Young supernova remnants shine strongly in X-rays primarily because of the intense heat generated by their expansion. As the gaseous shell ejected during a supernova explosion sweeps outward at speeds of several thousand kilometers per second, it accumulates and compresses surrounding interstellar gas.12
This process creates a powerful shock wave that heats the gas to temperatures as high as 10,000,000 K, which is sufficient to produce significant X-ray emission. During the initial stage of a remnant's evolution—which typically lasts several hundred years—the shocked gas is heated to these extreme temperatures and is most readily visible in the X-ray spectrum.21
While some remnants, such as the Crab Nebula, also emit X-rays through synchrotron radiation produced by high-speed electrons from a central pulsar, the X-radiation from most other supernova remnants emanates from this hot, shock-heated gas.12